Extension roller screen



March 22, 1960 s. K. MAHLOUFF 2,929,444

sxmusxou ROLLER SCREEN Filed Feb. 28, 1958 4 Sheets-Sheet 1 Salomon If. MAIILN/FF March 22, 1960 s. K. MAHLOUFF EXTENSION ROLLER SCREEN 4 Sheets-Sheet 2 Filed Feb. 28, 1958 Solomon K IVA/l0;

March 22, 1960 s. K. MAHLOUFF 2,929,444

EXTENSION ROLLER SCREEN Filed Feb. 28, 1958 4 Sheets-Sheet 3 March 22, 1960 s. K. MAHLOUFF 2,929,444

' EXTENSION ROLLER SCREEN Filed Feb. 28, 1958 4 Sheets-Sheet 4 12...HmmuItH\U 2 LIL 5m )r. mmarr EXTENSIONROLLER SCREEN I Salomon K. Mahloufi, Montreal, Quebec, Canada, as-

signor of twenty-five percent to Frank C. Teuzer, Sa nte Agathe des Ivlonts, Quebec, and nine percent to Laurent Martellin'o, three and one-half percent to Jean K.

Malouf, two percent to Leo Lafreniere, and two percent to Andre Nantel, all ofrMontreal, Quebec, Canada Application February 28, 1958, Serial No. 718,210 4 Claims. (Cl. 160-28) The present invention relates to improvements in roller screens for windows in'which the screening material s unwound from a tension roller as the sash is raised and conversely is wound on the roller as the sash is lowered.

The present invention is more particularly concerned with a roller screen of the adjustable type to be usedin connection with windows of various widths.

Several different types of extension roller screens are already known in the trade such as, for instance, the adjustable window screen illustratedand described in US. Patent No. 2,769,490 of November 6, 1956 by the present inventor. However, in all previously known constructions special side guards have to be securedalong the sides of the window frame to contact the lateral marginal portions of the window screen so as'to completely prevent entry of insects and the like through small openings.

Accordingly, the general object of the present invention is the provision of an extension roller screen of the character described in which the top screen frames and bottom screen housings between which the screening is attached for vertical adjustment, are so constructed and arranged that the lateral portions of the screening are in direct contact with the sash guiding rails of the window frame whereby the screening is completely sealed and no side guards or other additional elements are needed for sealing the screen.

-Another object of the present invention is the provision of an extension rollerjscreen in which the bottom screen housings are so arranged as to provide guiding means for the two separate-lengths of screening such as to maintain the same in good sealing contact at their overlapping portions'and yet to permit relative lateral adjustment of the roller screens to fit windows ofdifferent widths.

Yet another important object of the present invention is the provision of simple means in an extension roller fran nes which are adapted to be removably attached to the lower transverse member of the inner sash of the window and which are so designed as to guide the lateral portions of the screening along the conventional sash guiding rails of the window frame.

Yet another important object of the present invention is the provision of an extension roller screen of the character described which is so arranged that it can be locked in adjusted extended position by means accessible only from the inside of the Window.

The foregoing and other important objects of the pres- United States PatentO a edges between frame 3 and housing 5.

2,929,444 Patented Mar. 22, 19st) ice frames, which are adapted to be secured tothe lower transverse member of the inner sash, are adapted to overlap the outside lateral face of the intermediate'railsof the window frame so that the screen may slide directly on said lateral faceto effect sealing of the screen;

Figure 2 is an exploded perspective view showingrthe bottom screen housings in non-assembled position;

Figure 3 is an elevation of the assembled bottom screen housings looking at the inner face thereof;

Figure 4 is a cross-section along line 4-4 of Figure 3; Figure 5 is a cross-section along line 5-5 ofFigureB; Figure 6 is a cross-section along line 66 of Figure 3; s Figure 7 is a cross-section along line 7-7 of Figure'3; Figure 8 is a cross-section along line 88 of 'Figure' 'i; Figure 9 is an elevation lookingat the inside face of the outside end wall of the outer bottom housings;

Figure l0'is an elevation of the outside face of the outside end wall associated with the inner bottom housing; Figure 11 is a partial cross-section of the'lower transverse member of the inner sash showing howthe-upper frames for the screening are attached to said transverse member; i

Figure 12 is a front elevation of the same elements shown in Figure'll; Figure 13 is a cross-section of the same elements shown in assembled position; Figure 14 is a perspective view, partly in cross-section, of the intermediate partition plate used in the bottom screen housings;

Figure 15 is an elevation, partly in longitudinal section, of'the spring assembly for tensioning the screen roll and for urging the roll in journaled position; Figure 16 is a perspective view of a-pawl'element used in the assembly of Figure 15; and

Figure 17 is a cross-section of the end wall ,ofa housing member showing how a longitudinal wall of said throughout, reference numeral 1 generally indicates a,

two-way adjustable screen, including a pair of upper frames 2 and 3, of plastic, aluminium or other like durable material, slidable relative to one :another for lateral adjustment of the screen, and a pair of lower housings 14 and 5 also of plastic, aluminium or other light durable material, laterally slidable relative to one another in .cooperation with the upper frames. V 1 j A pair of flexible screening strips 6 and 7 are disposed in face to face relation, strip 6 being secured at its upper and lower edges between frame'Z and housing 4 and strip 7 being secured at its upper and lo I Each screen 3 strip 6 and 7 is slidable relative toeach other with the respective frame and housing to which it is secured jfor lateral adjustment of the screen 1'. r j v i I i As shown in"-Figure 1, the assembly of the lower housings 4 and 5 is disposed directly on top of the window sill A and the housings are longitudinally adjusted so that the outer ends thereof will abut directly against the inner faces of the lateral upright members 3 the outside upper sash. In Figure 1, only one upright lateral member B of the window frame is illustrated and the lower housing 4 enters the sash guiding channel defined by the outsidejrail C and the intermediate rail D so as to abut the inside face B'of the lateral frame member B of the window frame.

Each lower housing has such a width as to tightly or snugly fit in the guiding channel for the upper sash so that the inside face of the housing abuts against the lateral face D of the intermediate rail D. The housings are maintained in this position by means of strong spring clips 8 extending from the outside faces of the housings and engageable with the inner lateral face of the outside rail C, as shown in Figure 1. The clips 8 are preferably coated with neoprene or the like to prevent slipping. If desired, although not essential, the outside end plates 9 and 10 of the housings 4' and 5 re- .spectively are provided with points or the like projections 11 and 12, as shown in Figure 3, adapted to engage the wood of the inside face B of the lateral frame members B. Thus the lower housings 4 and 5 are positively secured directly on the window sill A and they are locked in this position by means described hereinafter.

As shown in Figure 6, the lower housings 4 and 5 are disposed side by side and each contains a roll of screening 13 and 14 respectively. The housings are provided with means for guiding the screening strips 6 and 7 to issue at the inner face of the housing assembly so that the screening strips are in contact with each other at their overlapping portions, and also such that they contact the lateral faces D of the intermediate rails D at both sides of the window frame. 7 Figure 13 shows a cross-section of the upper frames 2 and 3 which are in telescopic engagement, the frame 3 being engaged within the frame 2. The frame 2 simply consists of an elongated channel shaped member having inturned lips 15 and 16 at its top and lower edges respectively, the outer marginal portion of the lower lip 16 being extended andbent to form a bead 16' engaging the upper edge of the screening strip 6 thereby attaching said screening strip to the frame 2.

The upper frame 3 consists of an elongated strip profiled to form a channel with inturned top lip 17 and inturned bottom lip 18 engaging lips 15 and 16 of the upper frame 2 respectively. The upper lip 17 is extended and bent to form a horizontal shelf 19, while the bottom lip 18 is extended and bent to form an inverted U-shaped portion 18' terminated by a bead 20 disposed in side by side sliding contact with head 16' and in which the strip 7 is inserted and secured.

- A flexible sealing strip 21 made of rubbenplastic or the like, is secured to the shelf 19 and extends inwardly to engage the front face of the lower member E of the inner sash of the window. Similarly, a flexible sealing strip 22 is secured to the top portion of the outer frame 2, extends inwardly to engage the lower member E of the sash of the window frame and is in sliding operlapping contact with the strip 21.

The upper frames 2 and 3 are maintained in spaced relationship with respect to the sash member E by means of brackets 23 of L-shaped cross-section and which have a vertical leg provided with a slot 24 removably engaging the head of a screw 25 screwed in the outside face of the lower member E and projecting outwardly therefrom. To prevent disengagement of the bracketv 23 from screw 25, the slotted leg of bracket 23 is curved inwardly on one side of slot 24 as shown at 23' and either the head of screw 25 or the slotted leg of bracket 23 is coated with neoprene or the like.

The bracket 23 is provided at its outer end with oppositely directed tongues 26 respectively engaging the lips 17 and 18 of the inner frame 3 or the lips 15 and 16 of the outer frame 2, depending on the location of the brackets 23 with respect to the telescopically engaged frames 2 and 3. Thus the brackets 23 maintain the frames 2 and 3 in a position parallel toand spaced tion of the screening strip 6 or 7 can overlie the lateral face D of the intermediate rail D. The flexible sealing strip 21 or 22 contacts the transverse face of the rail D and may have a small extension to'contact the lateral face D. Thus any openings between the rails D and the screening strips 6 and 7 are completely sealed at each side of the window frame and along the member E of the lower sash.

Figures 11 and 12 show how the assembly of the sealing strips 21, 22, upper frames 2 and 3 and brackets 23 is held with two fingers and lowered so as to engage the screws 25 in the slots 24 of the brackets 23 to attach the assembly to the sash member E. There are preferably three or more brackets 23 along the length of the lower sash member E to properly secure the upper frames 2 and 3 in position on said sash member E.

The lower housings 4 and 5 will now be described in more detail.

Referring to Figures 2 to 10 inclusive, it will be seen that the housing 4 comprises an elongated sheet member bent to form a bottom wall 27, an outer wall 28 and top walls 29 and 30. The top wall 29 extends the entire length of the screen roll containing portion 4' of the housing, while the top wall 30 extends the length of the portion 4" of the housing containing the spring mechanism for tensioning the roll 13.

The top wall 29 has a width approximately twice the width of the housing 4, while the top wall 30 has a width substantially equal to' thewidth of the housing 4. Furthermore, the top wall 29 is at a slightly higher level than the top wall 30 for the insertion of a masking plate 31 (see Figure 5) which slidably engages a bead 32 at the edge of the top wall 29, and which is adapted to overlie the housing 5 and extends to the outerend of the latter where its downward lug 1' engages a groove at the top edge of the outside end'plate or wall 10 of the inner housing member 5, as shown in Figure 3, so as to secure the masking plate 31 to the housing 5.

The inner edge of the bottom wall 27 of the housing 4 is provided with L-shaped flange 33 extending the whole length of the housing.

An upright partition plate 34 is mounted within the housing 4 for longitudinal slidable movement therein;

said partition plate 34 divides the roll containing section 4' and the spring containing section 4" of the housing. More particularly, the partition plate 34 engages the walls 27, 28 and 3t), and the L-shaped flange 33. As shown in Fignirel4, said partition is provided in approximately the centre thereof with a circular boss 35 facing the spring housing section 4"; the boss 35 has a stepped bore forming a bore portion 36 of substantially large diameter facing the roll containing section 4' and a restricted diameter bore portion 37 opening into the spring housing section 4".

A spindle 38, on which the roll 13 is wound, is journaled at one end in the bore portion 36 and has an extension 39 of reduced diameter which passes through the reduced diameter bore 37 to project within the spring assembly.

As shown in Figure 15, a roll tensioning coil spring 40 engages at one end'a transverse hole made in the spindle extension 39 and at the other end a transverse hole made in a stud shaft 41. The coil spring 40 is theother end of the sleeve 42, surrounds the stud shaft 41sand at its other end .abuts against a radial flange 4, of the stud shaft 41.

As shown in Figures 15 and 16, the flange 44 of the studshaft 41 is' provided with a pawl tooth 45 engageable with any one of a plurality of ratchet teeth 44',

.made in a flange receiving cavity 45' of the end plate 46 of the housing 4.

As shown in Figure 2, the outer end portion of the stud shaft 41 extends through a bore made in the end plate 46 and is provided with a transverse groove 41' for receiving a screw driver or the like, whereby the stud shaft 41 may be rotated by simultaneously pressing and rotating the same so as to more or less tension the icoilspring 40 to impart the desired tension on the screeninglstrip .6. The engagement of the pawl tooth 45 with one of the ratchet .teeth in end plate 46 maintains the desired rotational tension in the coil spring 40.

The pressure spring 43 serves to maintain the pawl tooth 45 engaged with the ratchet teeeth of the end plate 46 and also urges the whole assembly of the sleeve 42, partition plate 34, spindle 38 and roll 13 away from the end plate 46 so as to maintain the other end of the roll 13 in journalled engagement with end plate ,9 at the other end of the housing 4.

Referring to Figure 9, the end plate 9 forms a thick portion 47, a thinner upper portion 48 and a thicker outer portion 47. The head 32 of the top wall 29 of the housing 4 engages a slot 49 made at the top. edge of the thin portion 48 of the end plate 9 and the end of the top wall 29 overlies the top edge of the portions .47 and 48, while the outer lateral wall 28 of the housing engages a shoulder Strand the bottom wall 27 engages .a shoulder 51 of the end plate 9. Similarly, the L-shaped flange 33 of the bottom wall 27 engages a rib 52 formed by the thicker portion 47' of the end plate 9. The end plate 9 is secured to the walls '27, 28 and 29 of the housing by snap locks such as shown in Figure 17; triangularly shaped bosses 53 are disposed at three edges of the end plate 9 and are each engageable with an opening 64 made in the corresponding longitudinal wall adjacent its end.

The parts 47, 47' of the end plate 9 are provided with a central cavity 54 of substantially circular shape for receiving the screen roll 13; said cavity 54 opens at the top edge of the part 47. The cavity 54 is provided at the centre thereof with a bore 55 for receiving the projecting end of the spindle 38 for the screen roll 13.

It will be noted that the end plate 9 is about twice the width of the housing 4 proper and is adapted to fit in the guiding channel of the outer window sash between the rails C and D with the inner edge 56 of the end plate 9 engaging the lateral face D of the rail D.

Referring to Figure 7; it will be seen that the screening strip'6 is guided from the roll 13 over an L-shaped guiding member 57, extends underneath the top wall 29 and slides against the bead 32 of said top wall. The lateral marginal portion of the screening strip 6 issues from the cavity 54 and extends over part 47 close to part 48 of end plate 9 so as to overlap and contact the lateral face D of the rail D when issuing from the housing 4. The L-shaped strip 57 engages a groove 58 in the end plate 9 and extends the entire length of the roll containing section 4 of the housing E and at its other end engages a head 59 formed at the edge of the top wall 30, said head 59 being shown in Figure 5.

The end plate 46, at the opposite end of the housing .4, is fastened to the housing by snap locks 64 similar to the one shown in Figure 17. The ends of the walls of the housing engage shoulders made around the periphery of the end plate 46 along three sides of the latter.

Referring to Figure 2, the inner housing 'is provided spending to the end plate 9 of the housing 4, adapted to engage between the rails C and D at the other side of the window frame.

An elongated sheet member is bent to provide a top wall 70, an inner lateral wall 71 and a bottom wall 72. The top wall is substantially the same width throughout the length of the housing. The longitudinal walls 70, 71 and 72 are secured to the end plates 10 and 46' by means of snap locks 64 similar to the one shown in Figure 17. The inner lateral wall 71 is slit, as shown at 73, the entire length of the section of the housing containing the roll 14 to provide for the passage of the screening strip 7. The bottom wall 72 extends the whole length of the housing and has an L-shaped flange 74.

The sheet member also provides an outer lateral wall 75 extending the wholelength of the roll containing section of the housing and leaving a slit 75 between said outer lateral wall 75 and the inner portion of the L- shaped flange 74 for the free slidable longitudinal movement of a hook 76 depending from the inner edge of the end plate 46 of the housing 4 and engaging the L- shaped flange 74 of the housing 5. The end plate 46' of the housing 5 is also provided' with a hook 77 engageable with the flange 33 of the housing 4; thus the two housings are maintained in side by side relationship and are slidable longitudinally with respect to each other. Notches 78 and 79 are made in the L-shaped flanges 33 and 74 respectively, for the engagement of the hooks 77 and 76. Once the two housings are longitudinally adjusted in accordance with the width of the window frame, said two housings are locked in position by means of a .bolt 80, shown in Figure 5, which passes through and is threaded within the lower portion of the end plate 46' of the housing 5, with its outer end adaptedto abut against the flange 33 of the housing 4. The bolt 80 is provided with a knurled head 81 projecting at the inside lateral wall 71 of the housing 5 and thereby accessible from the inside of the window. When locked in position by means of the locking bolt 80, the two housings cannot be removed from the outside of the window and, therefore,

cannot be stolen because once the inner sash is locked in lowered, window closing position, the knurledihead 81 is not accessible due to the very narrow space between the window sash and the assembly of housings 4 and 5, said space corresponding to the width of the intermediate rail D.

The arrangement of the housing 5 is the same as for housing 4; the screen roll 14 is mounted on a spindle 65,

; similar to spindle 38, is pushedsin a journalled position .in the end plate 10 of the housing 5 and is urged to notate by means of a spring mechanism similar to that described in relation to housing 4, said spring mechanism including a spring 87 similar to spring 40 enclosed in sleeve member 82 as shown in Figures 2 and 3, and a pressure spring and a flanged stud shaft 86 corresponding to spring 43 and stud shaft 41 of the housing 4. The outerend of spindle 65 engages a bore 66 made in end plate 10 and the walls 70, 71, 72 and 75 of housing 5 engages shoulders defined by a thicker portion 67 at the inner face of end plate 10 (see Figure 10). The partition plate between the spring mechanismand the screen vroll 14' is indicated at 83 in Figures 2 and 3 and is longitudinally'displaceable along the housing sufficiently to push the roll 14 into journalled position. The screening strip 7 issues through the slit 73 and extends in contact with the screening strip '6 in the overlapping portions of said screening strips, as clearly shown in Figures 4 to 6.

In the portion of the screening strip 7 not overlapping the screening strip 6, the strip 7 is guided directly by the bead 84 at the free edge of the top wall.

.Tofacilitate endwise adjustment of the screen 1 to it the width of the window frame the following procedure is preferred; the screen 1 is laid on the window sill A in its closed position with the screening strips 6 and 7 completely reeled and the outer lateral faces .of the upper frame members 2 and'3 flat against the top wall portion 29 of housing member 4 and the masking plate 31. In this position upstanding lugs 87 and 88 at the outer ends of the top wall portion 29 and masking plate 31 respectively (see Figures 1 and 3) removably engage holes made in the outer ends of the upper frame members 2 and 3, one of said holes being shown at 89 in Figure 1. Thus each housing member is slidable as a unit with its associated upper frame member relative to the other housing member and associated upper frame member.

While a preferred embodiment in accordance with the present invention has been illustrated and described, it is understood that various modifications may be resorted to without, departing from the spirit and scope of the appended claims.

I claim; 1

1. In combination with a sash typewindow, a screen construction comprising a pair of upper frame members arranged in telescopic engagement for sliding endwise adjustment to each other, bracket means securing said upper frame members near the bottom of the outer face of the lower window sash in outwardly spaced relationship therewith such that the outer ends of said upper frame members overlap and slidably contact the outer lateral faces of the sash guiding rails associated with said lower window 'sashon the outside'of the latter, sealing strips secured to said upper frame members and contacting the outer face of said lower sash member, a pair of screen housing members arranged in side-by-side horizontal relation and united along their adjacent side edges for sliding endwise adjustment relative to each other in cooperation with the corresponding upper frame members, a screening strip secured at one end to one of said upper frame members and inserted at its other end in the corresponding housing member, and a second screening strip normally disposed in'overlapping relation with said first strip and secured at one end to the remaining upper frame member and inserted at its other end in the remaining corresponding housing member, roller means mounted in said housings for separately reeling and unreeling said screening strips to facilitate adjustment as to the height of said screening strips, the outer end of each housing member fittingw'ithin the guiding channel for the upper window sash disposed outwardly of and adjacent the window sash provided with said bracket means and said roller means adapted to overlap the outer lateral faces of said rails so that the marginalouter portions of said screening strips will also overlap said outer lateral faces and said housbersj overla'p and slidably contact the outer lateral faces of the sash guiding rails associated with said lower window sash on the outside of the latter, sealing strips secured to said upper frame members and contacting the outer face of said lower sash member, a'pair of screen housing membersiarranged in side-by-side' horizontal relation and ings having guiding means for guiding said screening strips n with their marginal portions in sliding contact with said lateral faces; wherein the inner housing member, disposed next to the window sash, has an inner side wall in contact with the lateral faces of said rails and a top wall defining with said inner side wall a longitudinally inside top corner and further has a top wall portion above theroll of screenings'trip, said top wall portion having an extension overlying and spaced from the top wall of the inner housing member, and terminating at its free edge in substantial alignment with the inner lateral face of said inner housing member, whereby said guiding member and the free edge of the top wall of said outer housing member guides the screening strip associated with said outer housing member to issue from the assembly of housing members in substantial alignment with the inner side wall of said inner housing member.

2. In combination with a sash type window, a screen construction comprising a pair of upper frame members frame members near the bottom of the outer face of the lower window sash in outwardly spaced relationship therewith such that the outer ends of said upper frame memarranged in telescopic engagement for sliding endwise ad- 'justment to each other, bracket means securing said upper united along their adjacent side edges for sliding endwise adjustment relative to each other in cooperation with the corresponding upper frame members, a screening strip secured at one end to one of said upper frame members and inserted at its other end in the corresponding housing member, and a second screening strip normally disposediin overlapping relation with said first strip and secured at one end to the remaining upper frame member and inserted at its other end in the remaining corresponding housing member, roller means mounted in said housings .for separately reeling'and unreeling said screening strips to facilitate adjustment as to the height of said screening strips, the outer end of each housing member fitting within the guiding channel for the upperrwindow sash disposed outwardly of and adjacent the window sash provided with said bracket means and said roller means adapted to overlap the outer lateral faces of said rails so that the marginal outer portions of said screening strips will also overlap said outer lateral faces and said housings having guiding means for guiding said screening strips with their marginal portions in sliding contact with said lateral faces; wherein each of said housing members comprises an outer end wall and an inner end wall, a section containing the roll of screening strip adjacent said outer end wall, and a section containing a spring mechanism adjacent said inner end wall, a partition plate separating said two sections and arranged for longitudinal movement within the housing member, a spindle on which said roll of screening strip is wound, said spindle having one end journalled in, said outer end wall of said housing and the other end journalled in said partition plate and projecting therethrough, said spring mechanism comprising a first coil spring connected to the projecting end of said spindle, pawl and ratchet means connected to the other end of said coil spring for adjustably tensioning said coil spring, said pawl and ratchet means comprising a stud shaft having a flange provided with a pawl tooth on one face thereof, said inner end wall having a cavity for receiving said flange, said cavity having ratchet teeth for engaging the pawl tooth of said flange, said inner end wall further having a bore through which said stud shaft projects to the exterior of the housing member, and a sleeve member enclosing said first coil spring and abutting said partition plate atone end and a second coil spring abutting the other end of said sleeve member and the flange of said stud shaft, to urge said partition plate and the spindle of said screen roll in a direction towards said outer end wall, and to urge said pawl against said ratchet.

- 3. In combination with a sash type window, a screen construction comprising a pair of upper frame members arranged in telescopic engagement for sliding endwise adjustment to each other, bracket means securing said upper frame members near the bottom of the outer face of the lower window sash in outwardly spaced relationship therewith such that the outer ends of said upper frame members overlap and slidably contact the outer lateral faces of the sash guiding rails associated with said lower window sash on the outside of the latter, sealing strips secured to said upper frame members and contacting the outer face of said lower sash member, a pair of screen housing members arranged in side-by-side horizontal relation and united along their adjacent side edges for sliding endwise adjustment-relative to each other in a screening strip secured at one end to one of said upper I frame members'and inserted at its other end in the corresponding housing member, and a second screening strip normally disposed in overlapping relation with said first strip and secured at one end to the remaining upper frame member and inserted at its other end in the remaining corresponding housing member, roller means mounted in said housings for separately reeling and unreeling said screening strips to facilitate adjustment as to the height of said screening strips, the outer end of each housing member fitting within the guiding channel for the upper window sash disposed outwardly of and adjacent the window sash provided with said bracket means and said roller means adapted to overlap the outer lateral faces of said rails so that the marginal outer portions of said screening strips will also overlap said outer lateral faces and said housings having guiding means for guiding said screening strips with their marginal portions in sliding contact with said lateral faces; wherein the outer one of said housing members comprises a top wall made in two sections and extending over two longitudinal sections of said outer housing member, one portion of said top wall terminating in substantial alignment with the inner lateral face of said outer housing member and the other portion of said top wall extended inwardly to terminate in substantial alignment with the inner lateral face of ill the inner one of said housing members, the top wall portions of said outer housing member being slightly vertically spaced, and further including a masking plate in serted between said two top wall portions, said masking plate having a width substantially equal to the overall width of the assembly of said housing members and extending up to the outer end wall of said inner housing member.

4. The combination claimed in claim 3, wherein said masking plate and said outer end wall of said inner housing member have interlocking means for fastening said masking plate to said outer end wall.

References Cited in the file of this patent UNITED STATES PATENTS 2,026 Briggs July 11, 1865 998,102 Ladwig et al July 18, 1911 1,252,286 Masson Jan. 1, 1918 2,207,856 Gieser July 16, 1940 2,769,490 Mahlouff Nov. 6, 1956 

